IS 1646: Code of practice for fire safety of buildings (general): Electrical installations

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IS 1646: 1997
( Reaffirmed 2002 )

Indian Standard

CODE OF PRACTICE FOR

FIRE SAFETY OF BUILDINGS (GENERAL):

ELECTRICAL INSTALLATIONS

( Second Revision )

ICS 91.120; 13.220.50

©BIS 1997

BUREAU OF INDIAN STANDARDS

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

June 1997 Price Group 8

Fire Safety Sectional Committee, CED 36

FOREWORD

This Indian Standard (Second Revision) was adopted by the Bureau of Indian Standards, after the draft
finalized by the Fire Safety Sectional Committee had been approved by the Civil Engineering Division
Council.

This standard was first published in 1961, revised subsequently in 1982. The present revision is based on
the subsequent development and modifications in other regulations such as electrical rules of the Tariff
Advisory Committee, Indian Electricity Rules, etc, and other Indian Standards. Special precautionary
measures for use of aluminium conductors and for use of fluorescent fittings in electrical installations are
included in the revision. The other changes relate to the developments in wiring methods and other
general aspects.

The requirements of this code are to be treated as supplementary to the requirements of the Indian
Electricity Act, 1910 and the Rules of 1956 thereunder and in no case as substitutes. In the preparation
of this code, it has been presumed that the electrical installation work is carried out by qualified
contractors and electricians under the supervision of competent engineers as required by the Indian

Electricity Rules,

For the purpose of deciding whether a particular requirement of this standard is complied with, the
final value, observed or calculated, expressing the result of a test, shall be rounded off in accordance with
IS 2 : 1960 'Rules for rounding off numerical values (revised)'. The number of significant places retained
in the rounded off value should be the same as that of specified value in this standard.

IS 1646 : 1997

Indian Standard

CODE OF PRACTICE FOR

FIRE SAFETY OF BUILDINGS (GENERAL):

ELECTRICAL INSTALLATIONS

( Second Revision )

1 SCOPE

This standard covers recommendations relating to
fire safety of electrical installations in buildings.

2 REFERENCES

2.1 The Indian Standards listed in Annex A contain
provisions which, through reference in this text,
constitute provisions of this standard. At the time
of publication, the editions indicated were valid.
All standards are subject to revision, and parties to
agreements based on this standard are encouraged
to investigate the possibility of applying the most
recent editions of the standards given in Annex A

3 GENERAL REQUIREMENTS

3.1 Besides conforming to this Code all equipment
shall comply with relevant Indian Standard
Specifications (wherever available) as regards con-
struction, temperature rise, current rating, over-
loads and performance, etc, where an Indian
Standard does not exist the various items of electri-
cal equipments should be those approved by the
competent authority.

3.2 Execution of work unless otherwise exempted
under the appropriate rule of the Indian Electricity
Rules, the work of electrical installations shall be
carried out by an electrical contractor licensed and
under the direct supervision of a person holding a
certificate of competency and by persons holding a
valid permit issued and recognized by any Indian
Government.

3.3 All equipment shall be capable of developing
and/or consuming the rated power safely and con-
tinuously (unless specifically meant for intermitent
use), without undue heating, sparking, noise and
vibration.

3.4 All electrical equipment shall be securely
mounted on the surface on which they are installed.

3.5 All electrical equipment, fittings, accessories
and wiring systems in locations which are exposed
to the following shall be of types approved for

particular situations and subject to special condi-
tions as laid down in the appropriate clauses of this

code:

a)
b)

c)
e)

Fumes;

Flammable or other gases, vapours or li-
quids having deleterious effect on equip-
ment and conductors or creating dangerous
situations;

Dust and fibrous accumulations;
Damp or wet locations; and
Excessive temperature.

3.6 Manufacturer's name, trade-mark or other
description markings by which the manufacturer
may be identified shall be placed on all electrical
equipment, accessories, electrical cables, etc.
Other markings like voltage current and wattage
shall also be provided as necessary. Marking shall
be of sufficient durability to withstand the environ-
mental conditions.

3.7 The type of wiring installed in a particular
occupancy shall be as permitted under the relevant
provisions of this standard.

3.8 Where aluminium conductors are used in the
electrical installation, special precautionary

measures as given in IS 732 shall be followed.

4 POWER EQUIPMENT

4.1 The term power equipment shall be deemed to
include motors, motor-generators, control gears,
switch gears, rotary convertors, rotary balancers,
rotary condensers, phase advancers, frequency
changers and any other rotating electric equipment,
rectifiers and inverters.

4.2 All electrical equipment located in situations
where:

a) The atmosphere is likely to contain flam-
mable/explosive gases or vapours; and

b) Combustible dust, fluff or similar materials
like saw mills and other wood working oc-
cupancies, cotton/jute/wooden/viscose and

IS 1646 : 1997

acrylic, nylon 66 fibre mills, flour mill, pul-
verising works, etc, shall comply with the
special requirements in respect of Hazard-
ous Location specified in 13.

4.3 Equipment which depends on natural air for
cooling shall be so located and installed that air
flow over the exposed cooling surface shall not be
prevented by adjacent equipment or walls. For
floor mounted equipment, clearance between top
surface of the equipment and the adjacent surface
shall be provided to dissipate rising hot air.

4.4 Equipment ventilating openings shall be so
installed that no obstruction may prevent free air
circulation through them; nor shall any material be
dumped or allowed to settle on them so as to clog
the ventilation openings or interfere in any way
with normal cooling of such equipment.

4.5 All equipment of more than 1/4 kW shall be
separated from unprotected woodwork by a dis-
tance of at least 300 mm horizontally and 1 200 mm
vertically. Equipment of 1/4 kW or less, except
those of totally enclosed type, shall be suitably
guarded to avoid heat being transmitted to readily
combustible material in the vicinity.

4.6 Equipment shall be periodically inspected and
maintained as per relevant Indian Standards by
competent staff who shall keep complete records of
all such activities.

4.7 The position of equipment shall be selected
with due consideration of accessibility, main-
tenance and overhaul.

4.8 Equipment terminals shall be rigidly designed
and planned according to size and type of machine.
Industrial motors shall have a robust metal clad
terminal box of adequate dimensions arranged to
receive armoured or vulcanized rubber insu-
lated/PVC cables in conduits without unnecessary
bends in the cables. All terminal boxes shall be
entirely reptile, rodent and insect proof.

5 SWITCHBOARDS

5.1 Switchboards shall be erected in easily acces-
sible and approved positions where cotton fluff,
dust or dirt is not present. The switchboard shall
be located in dry locations.

5.2 The space around the switchboards shall not be
used for storing of clothing or other materials, even
for temporary period.

5.3 Each outgoing circuit from the switchboard
shall be separately controlled by a suitable auto-
matic circuit breaker or linked switches and cut-
outs. In case the electrical installation draws power
from a distribution transformer having a capacity
of 150 kVA or more, the switches shall be provided

with HRC fuses at all fuse points, irrespective of
current rating of the circuit. This, however, need
not be insisted in case of low tension installation.

5.4 All switches and circuit breakers shall be
operated from the front of the switchboard.

5.5 All fuses shall be mounted on the front of the
switchboard as far as practicable.

5.6 All screws, bolts and nuts, which secure current
carrying parts to the board shall be of brass, copper
or similar rustproof material.

5.7 All wires and cables shall be provided with
soldered or approved lugs or crimped joints or any
other approved means of connection.

5.8 In situations where the atmosphere is likely to
contain explosive gases or vapour, switchboards
shall be of explosion protected type. Selection of
electrical equipment shall be as per IS 5571 (see
also IS 5572 for classification of hazardous areas).
Alternately pressurised air lock enclosures may be
provided for switchrooms. Wherever not possible
switchroom should be themselves pressured.

5.9 Where the switchboard is erected in a room of
a building isolated from the source of supply or at
a distance from it, adequate means of control and
isolation shall be provided both near the boards and
at the origin of supply.

5.10 All switchboard shall be of metal clad totally
enclosed type or any insulated enclosed pattern
which should be fixed at close proximity to the point
of entry of supply.

5.11 In case of outgoing circuits from the
switchboard, where the current rating exceeds 63 A,
connection between the busbar chamber and the
automatic circuit breaker or switch fuse or any
other control gear shall be made only by solid con-
nections.

5.12 Timber shall not be used in construction of a
switchboard.

5.13 All circuits shall be clearly and indelibly
labelled for identification in English and ver-
nacular.

5.14 Moulded case circuit breakers shall not be
permitted except inside a metal enclosure.

5.15 The neutral of each main and branch main
circuit shall be provided with a removable link
placed in an easily accessible position, for purpose
of testing. The neutral shall not be punched at the
back of the board.

IS 1646 : 1997

6 POWER DISTRIBUTION AND MOTOR
CONTROL GEAR

6.1 All equipment shall be of metal clad construc-
tion throughout, dust tight, suitably proportioned
and of adequate capacity and shall conform to the
relevant Indian Standards.

6.2 Equipment shall be accessible at all times,
stacks of goods and the like shall not impede access
to any part of the equipment.

6.3 Wiring to and from the gear shall be of the
armoured, mineral insulated or screwed steel con-
duit type and provision shall be made to secure the
same by approved and efficient mechanical
methods. Flexible tubing shall not be accepted for
general wiring. It may, however, be used for con-
nections between the terminal boxes of motors and
starters, switches and motors but the length shall be
restricted to a maximum of 1 200 mm.

NOTE — Non-metallic conduits conforming to IS 9537
(Part 3) may be used for medium voltage installation, subject
to following conditions:

a) The conduits should be supported not more than 800
mm distance and should have suitable joints.

b) Separate earthing conductor shall be run inside the
conduit for earthing the equipment to which the con-
ductor is connected.

c) Expansion joints shall be provided where required to
compensate for thermal expansion and contraction.

Such non-metallic conduit shall not however be allowed in
following locations:

a) In locations less than 2.5 m above walking floor level
unless protected against mechanical damage.

b) Where ambient temperature is likely to be above 55°C
at some time or other during year.

c) In concealed places of combustible construction.

d) In locations where the atmosphere is likely to contain
flammable gases or vapours.

e) In locations where the surrounding atmosphere is likely
to affect the non-metallic conduits.

6.4 The ends of all conduits shall be bushed.

6.5 All unused cable holes shall be effectively
closed.

6.6 All current carrying parts, namely terminals,
washers and clips shall be of copper, brass or of any
other equally non-rusting material, properly tinned
at joints.

6.7 All cables shall be provided with soldered lugs
or other approved means for connection.

6.8 Where a distribution board or group of dis-
tribution boards is/are erected in a room of a build-
ing isolated from the source of supply, adequate
means of control and isolation shall be provided
both near the board and at the origin of supply.
Similar means of control and isolation shall be
provided even if the source of supply and the dis-
tribution board(s) is/are located inside the same

compartment but separated from each other by
more than 15 m.

6.9 Outgoing circuits shall be clearly marked in
English and vernacular, indicating the department
or place or item controlled, by each.

6.10 All circuits shall be arranged symmetrically,
as far as practicable.

6.11 Each circuit from a main distribution board
shall be provided with a circuit breaker, linked
switches or cut-outs.

6.12 Looping of conductors and tee joints in power
wiring shall be provided with a circuit breaker,
linked switches or cut-outs.

6.13 Detachable inspection covers shall be
provided to examine connections.

6.14 Woodwork shall not be permitted for mount-
ing of or construction of frame work of any iron-
clad switch control or distribution gear.

6.15 Motors shall not be connected to lighting dis-
tribution boards.

6.16 Suitable guard enclosures shall be provided to
protect exposed current carrying parts of motors
and insulations of motor leads where installed
directly under equipment or in other locations
where dripping or spraying of oil, water or other
injurious liquids may occur, unless the motor is
designed for such conditions.

6.17 In situations where dust or flying materials
may collect on or in motors in such quantities as to
seriously interfere with ventilation or cooling of
motors, totally enclosed or totally enclosed fan-
cooled motors that will not overheat under prevail-
ing conditions, shall be used.

7 TRANSFORMER SUBSTATION,
EXCLUDING BELL AND DRAWING FRAME,
TRANSFORMER AND TRANSFORMERS OF
SMALL CAPACITY

7.1 Every oil-filled apparatus, such as transformer,
static condenser, switchgear or oil circuit breaker
having an individual or aggregate oil capacity of
2 000 litres or more shall be housed in a locked,
weather and fire resistant building and shall be
properly ventilated to the outside of the building
only. The building housing the oil-filled apparatus
shall be separated by a distance of not less than 6 m
from all other buildings.

NOTES

1 If the building housing the transformer is within 6 m of the
surrounding building there shall not beany door or window
opening in the substation or the surrounding building.

2 If the building or compartment housing oil-filled ap-
paratus is communicating with another building or com-

IS 1646 : 1997

partment, the substation shall be segregated by separating
walls of 355 mm thick brick wall or 230 mm thick RCC,
carried up to roof level with door openings therein protected
by single fireproof doors of 2 h rating.

3 Not withstanding the above, if the substations supplies
power to fire pumps, the same shall be segregated from, the
adjoining building by 400 mm thick brickwall or 300 mm thick
RCC wall without any door opening therein where, however,
dooropenings are absolutely necessary, the openings shall be
protected by double fire resisting doors of 2 h rating each. If
the substation is attached to a storeyed structure, in addition
to segregations, it will also be necessary for the substation to
be provided with RCC slab roof.

7.2 Each oil-filled apparatus, such as transformer,
bank of static condensers, including high tension
circuit breakers, switch and main distribution
boards, having an individual or aggregate oil
capacity of 2 000 litres, shall also be segregated from
all other apparatus by 355 mm thick fire resisting
brick wall or 230 mm thick RCC. The separating
wall shall be carried right up to the roof level unless
the roof is more than 3 m above the highest point
of the equipment, in which case the wall shall be
carried up to a height at least 600 mm above the top
of the equipment so separated.

NOTES

1 This provision need not be applied to furnace and rectifier
transformers as also to transformers of testing apparatus or
other equipment of which the transformer is an integral part,
whether they are oil-filled or not.

2 The requirements given under this rule, however, do not
apply to dry type transformers, or transformers having sul-
phur hexafluoride, non-flammable coolants and having
primary voltage not more than 33 kV.

3 If the substation supplies power to fire pumps, separating
walls as described above will be necessary between the
various items irrespective of the oil contents.

7.3 Each building or compartment housing oil-
filled apparatus containing 2 000 litres or more of
oil shall be provided with oil drains of at least 150
mm in diameter and soak pits, the latter being not
less than 2.5 m away from the substation. Floors
shall be sloped not less than 1 in 96 towards oil
drains. The soak pits shall be of sufficient capacity
to take the entire oil content of the equipment and
designed to provide for drainage of liquids to a safe
location.

7.4 A minimum clearance of 750 mm shall be
provided between the transformer or other ap-
paratus and enclosing or separating walls.

7.5 Substations and switchgear rooms shall only be
used to house the intended equipment. Storage of
any kind/or any repair work shall not be permitted
therein.

7.6 Suitable apparatus shall be provided in ap-
proved positions for the control and protection of
windings of transformers.

7.7 All transformers shall have suitable isolating
equipment on both high and low/medium tension
side.

7.8 Cable trenches inside substations shall be filled
with sand, pebbles or similar non-flammable
materials or covered with incombustible slabs. If a
number of cables are taken in a trench, it is
desirable that cables are taken on racks.

7.9 All control gears shall be protected against
rodents, reptiles and insects.

7.10 It is essential in all transformer houses and in
places of similar applications that an efficient and
distinctive indicating device be provided to show
clearly whether the supply in the main incoming
cable is 'On' or 'Off for the safety of fire-fighting
personnel in the event of an outbreak of fire.

7.11 Transformers and equipment installed out-
doors, having an individual or aggregate oil content
of 2 000 litres or more shall be located in a suitably
fenced and locked enclosure separated on all sides
by at least 6 m from any building including substa-
tion. Separating walls are necessary between trans-
formers having an individual or aggregate oil
content of 2 000 litres.

NOTES

1 There should be no door or window opening in the sur-
rounding building, if the transformers are within 6 m thereof.

2 If the transformers are within 6 m of doors and window
openings of surrounding buildings then they shall be
protected by single fire proof doors and 6 mm thick wired
glass in steel frames respectively.

3 Separating walls shall not be necessary in case of trans-
formers having an aggregate oil capacity exceeding 2 000
litres but individual oil capacity of Jess than 5 000 litres if the
distance between transformers and other apparatus is more
than 6 m or if the transformers are protected by an approved
high velocity water spray system.

4 Where however oil capacity of individual transformer is
larger than 5 000 litres separating walls shall be provided
unless all equipment/building/plant are located at a clear
distance of not less than the following:

Oil Capacity of Individual Clear Separating

Transformer (t) Distance (m)

5 000-20 000 8

Over 20 000 15

5 The provisions of 7.1, 7.2, 7.3 and 7.11 are not applicable
if the transformer is filled with non-combustible insulant
liquid.

8 EARTH CONNECTIONS

8.1 All earth connections shall strictly comply with
IS 3043.

8.2 In no case shall gas, steam, sprinkler or
humidifier pipes be used for an earth connection.

9 WIRING METHODS

9.1 General Requirements

9.1.1 Only such wiring methods as are permissible
for a particular situation or location as laid down in
rules under this clause, shall be allowed.

IS 1646 : 1997

9.1.2 Wherever aluminium conductors are used,
the special precautionary measures laid down in
IS 732 shall be followed.

9.1.3 Conductors shall be insulated except where
enclosed or bare conductors are specifically per-
mitted under the rules.

9.1.4 Conductors exposed to oils, greases, vapours,
gases, fumes, liquids or other substances having
deleterious effects upon the conductor or its insula-
tion shall be of approved type for the purpose.

9.1.5 Conductors may be permitted to be con-
nected in parallel (electrically joined at two ends to
form a single conductor only) if such conductors are
of same length, material and cross -sectional area,
have same type of insulation and terminated in
same manner.

9.1.6 Where cables, conduits, cable ducts or trunk-
ings pass through floors, walls, partitions or ceil-
ings, the surrounding holes shall be made good with
cement or similar incombustible material to the full
thickness of floor, wall, etc. In addition where con-
ductors are installed in channels, ducts, trunkings
or shafts passing through floors, walls, partitions or
ceilings, suitable internal fire resisting barriers
shall be provided to prevent spread of fire from one
side to the other.

9.1.7 Cables of ac circuits installed in steel con-
duits, shall always be so bunched that the cables of
all phases and the neutral (if any) are contained in
the same conduit.

9.1.8 Ducts of metal or insulating material and
trunking shall be securely fixed and where they are
liable to suffer mechanical damage, shall be ade-
quately protected.

9.1.9 Trunkings shall be constructed of metal or
non-combustible insulating materials.

9.1.10 Cables, cable ductings or trunking of metal-
lic construction and conduits may be buried under-
ground provided they meet the following minimum
earth cover requirement:

Wiring Method Minimum Depth of

Earth Cover

Rigid metal conduits 150 mm

Other type of conduits 450 mm

Metallic ductings or 450 mm (with con-

trunkings crete envelope of not

less than 50 mm
around the ducting of
trunking)

Directly buried cables 600 mm

9.1.11 No wiring system of any kind shall be per-
mitted inside ducts needed for transporting dust,
loose materials or flammable vapours.

9.1.12 Electrical. services shall not be installed in
the same conduit or trunking as pipes or tubes or
non electrical services like air, gas, oil, water, etc.

9.1.13 Only PVC sheathed armoured cables or
rigid metallic conduits shall be allowed in ducts or
plenums used for movement of environmental air.

10 PERMITTED TYPES OF WIRING METHODS

10.1 General

10.1.1 Wiring shall be on distribution board sys-
tem with main, branch main and final sub-circuit
boards fixed at convenient positions and shall con-
form to IS 732.

10. 1.2 Conductors which are not arranged for con-
nection to the same system and circuit or which
supply different phases of the same supply, shall be
kept apart throughout their entire run. This shall
particularly apply to installations in which there are
pilot lights in addition to the main lighting and the
like.

10.1.3 Conductors for final sub-circuits shall not
be enclosed in the same conduit or casing as sub
main and branch of main conductors.

10.1.4 Conductors which pass through windows or
door frames, wood beams walls, ceilings and floors
shall be protected by porcelain tubes or conduits
according to the conditions. The tube or conduit
shall extend at least 13 mm on both sides of the wall
and 25 mm above the floor and below the ceiling.

10.1.5 All conduit ends shall be bushed.

10.1.6 Cables which are unarmoured shall be
mechanically protected up to a height of 1.8 m
above working floor level or up to the height of
switchboard.

10.1.7 Branch main and distribution boards shall
be mounted in suitable accessible positions, not
higher than 2 m above floor level. Adequate work-
ing spaces and freedom from danger shall be
provided.

10.1.8 Incoming mains shall be used for control of
circuit in conjunction with suitable circuit breakers.

10.1.9 The system of wiring and all other details
shall be suitable to the conditions prevailing.

10.1.10 Linked tumbler switches shall not be used
for control of circuits.

10.1.11 Flexible leads shall hang vertically
downwards from the ceiling rose without any
obstructions, shall not be in contact with shafting
structural member, pipe work, etc, and shall not be
coiled or tied up but cut to correct length.

IS 1646 : 1997

10.1.12 Flexible leads shall be renewed when they
show signs of deterioration. Joints in flexible con-
ductors of pendants shall not be permitted.

10. 1.13 Flexible leads shall not be used where they
are likely to swing due to ventilation or humidifier
apparatus or any other cause; fixed rod or conduit
protection shall be used in such cases.

10.1.14 Flexible leads and fittings shall not be
allowed to vibrate.

10.1.15 Ceiling roses shall be securely fixed and
shall be complete with caps.

10.1.16 Straight or slanting wall batten holder
shall not be fitted at switchboard height or on the
switchboard.

10.1.17 Shades or reflectors of light points shall
not be in contact with structural members, pipe
work, etc.

10.1.18 Temporary wiring shall not be permitted.

10.1.19 Pendants in close proximity to humidifiers
shall be provided with approved water-tight fit-
tings.

10.1.20 Only rod pendants shall be used in in-
dustrial buildings like textile mills, flour mills, saw
mills, etc.

10. 1 .2 1 In ducts and tunnels only bulk head fittings
with wires in conduits or armoured cables shall be
used for lighting.

10. 1 .22 The base of accessories shall be of vitreous
materials.

NOTES

t Bakelite ceiling roses may be permitted in industrial
buildings except in areas where the atmosphere is likely to
contain explosive gases or vapours.

2 Bakelite switches may be permitted in industrial buildings
except in 'Hazardous Locations' as defined later in this code.

10.1.23 Reflector fittings meant to be suspended
by chain shall not be suspended by string or any
other similar material.

10.1.24 Fittings for lamps in places where con-
siderable dust or fluff is present (such as willowing,
lap breaking, waste opening, mixing, blowing, and
raising rooms in textile mills, flour mills, saw mills
and other wood working factories, etc) shall be of
dust tight type conforming to IS 4013.

10.1.25 In situations where the atmosphere is
likely to contain explosive/flammable gases or
vapours, fittings of flameproof type shall be used
unless otherwise permitted under clauses relating
to 'Hazardous Locations'.

10.1.26 The run or course of wiring shall be
arranged to avoid crossing of belt drives; where

such crossing is unavoidable mechanical protection
shall be provided against damage by belt breakages.

10.1.27 The paper insulated lead covered cables
shall not be brought right through the sealing box
without a break. The conductors of paper insulated
cables shall be terminated in the trifurcating box
and tails of India Rubber (VIR) Conductors
sweated by ferrules to the conductors of paper
insulated cables shall be brought through the
trifurcating box.

10.1.28 All filament lamps shall be so placed or so
guarded as to prevent ignition of combustible
material. Any shade or guard used for this purpose
shall be suitable to withstand the heat of the lamp.

10.1.29 Wiring of lighting circuits shall be on
distribution board system and circuit diagrams shall
be attached to it.

10.1.30 Conductors shall be run as far as possible
along the walls and ceilings, so as to be accessible
for inspection.

10.1.31 Where two or more points are mounted,
with a voltage differences exceeding 230 V between
them, a minimum distance of 2 m between the
points shall be maintained to avoid possibility of

shocks.

10.1.32 Cord grips shall be provided for pendant
lamp holders of bayonet contact type, and chain
suspended reflector fittings shall have the cable
entries made bell-shaped or bushed to avoid
damaging the flexible cables.

10.1.33 Chain suspended fittings, fans, etc, shall be
fixed at a distance not exceeding 250 mm away from
ceiling rose.

10.1.34 Where long spans occur between beams
and supports, battens shall be provided for attach-
ment of conduits, casing, or other wiring or fittings.
The runners shall be of well seasoned teak wood,
free from shakes, splits, etc, and shall not be less
than following dimensions:

Span (m) Dimensions (mm)
1.2 to 1.8 75 x 38

1.8 to 2.4 75 X 50

2.4 to 3.4 75 x 63

3.4 to 4.4 100 x 75

Alternatively, they may be suspended from a
catenary arrangement or be supported on steel sec-
tions of suitable size.

10.1.35 The wiring for hot air chambers shall be
mounted on the walls outside the chamber, as far as
possible. The light fittings inside the chambers
shall be of oyster type or shall be waterproof
fittings.

IS 1646 : 1997

10.1.36 Where wiring is to be carried along the face
of rolled steel joists or stanchions, a wooden or
non-conducting backing, preferably of the full
width of joists or stanchions shall first be laid on the
joist or stanchions and secured rigidly thereto.
Wooden pieces for the support of casing or conduit
to steel joists or stanchions shall be secured by
metal clips with at least two screws.

10.1.37 Scaffolding ropes shall not be tied round
conduits, casings or other forms of wiring.

10.1.38 All strands of cables shall be fitted into
terminals of switches, fuses, etc; strands of cables
shall not be cut. In damp locations, the strands
shall be soldered together.

10.2 The wiring methods specified in 10.3 to 10.7
shall only be permitted subject to conditions stipu-
lated therewith.

10.3 Conduits

10.3.1 Conduits and fittings shall be of solid drawn
and welded steel of heavy gauge screwed type, con-
forming to IS 2667.

NOTE — Rigid non-metallic conduits conforming to IS 9537
(Part 3) may, however, be used for low and medium tension
installations except in locations mentioned under 9.3.5 and
subject to the following conditions:

a) Conduits should be supported not more than 800 mm
and should have suitable joints;

b) For earthing, separate earthing conductors shall be run
inside the conduit from end to end; and

c) Expansion joints shall be provided, where required, to
compensate for thermal expansion and contraction.

10.3.2 Solid drawn welded steel conduit shall be
permitted under all atmospheric conditions and in
all occupancies subject to stipulations laid down
in 10.3.3 and 10.3.4.

10.3.3 In damp situations, such as textile sheds, the
conduits shail be hot galvanized or zinc impreg-
nated or treated with special rust-proof paint.

10.3.4 In occupancies like chemical factories,
bleach and dye houses, where strong corrosive
vapours are present special conduits or conduits
with additional coatings of bitumen paint or with a
glass wool lagging provided with a protective
covering shall be used.

10.3.5 Non-metallic conduits shall not be per-
mitted in the following locations:

a) Where wiring height is less than 2.5 m above
working floor level, unless protected against
mechanical damage;

b) Where exposed to ambient temperatures
likely to be above 55 C at sometime or other
during the year;

c) In concealed places of combustible con-
struction;

d) Where the atmosphere is likely to contain
flammable gases or vapour;

e) Where conductor operates at voltage above
650 V; and

f) In locations where surrounding atmosphere
is likely to affect the non-metallic conduits.

10.3.6 Flexible conduits shall not be used for
general wiring. It may be, however used for connec-
tions between terminal boxes of motors and
starters, switches and motors but thelength shall be
restricted to a maximum of 1 200 mm.

10.4 Mineral Insulated and Other Types of Metal
Sheathed Cables

10.4.1 Mineral insulated metal sheathed cables
and other types of metal sheathed cables are per-
mitted under all atmospheric conditions and in all
occupancies except as mentioned hereunder:

a) Where they would be exposed to destructive
corrosive conditions.

b) Where directly buried under ground,
without suitable protection against
mechanical damage and corrosive condi-
tions.

c) Metal sheathed cables of other types shall
not be directly buried under ground, nor
shall they be used in wet locations unless:

1) the metallic sheath is impervious to
moisture,

2) a lead sheath or waterproof jacket is
provided under the sheath, and

3) the insulated conductors under the
sheath are approved for use in wet
locations.

10.4.2 In case of wet locations like in parts of
laundries, tanneries, etc, and in locations where
walls are frequently washed, a minimum clearance
of 6 mm shall be maintained between mineral
insulated cable and the wall to which it is affixed.

10.5 Armoured Cables

10.5.1 Armoured cables shall be permitted under
all atmospheric conditions and in all occupancies
except in commercial garages, storage battery
rooms and in locations where they would be ex-
posed to corrosive fumes or gases.

10.6 Tough Rubber and Other Non-metallic
Sheathed Cables

10.6.1 Tough rubber or plastic sheathed cables
shall not be permitted in the following locations:

a) Where considerable dust and/or fly in
generally present (for example cotton and
jute mills and other vegetable, fibre process-
ing factories, flour mills, saw mills and other

IS 1646 : 1997

wood working factories, plastic and rubber
goods factories, pulverising works, etc);

b ) Where atmosphere is likely to contain flam-
mable/explosive gases or vapours;

c) Where the hazardous trades or processes
are carried out (for example, oil mills, paint
and varnish factories);

d) Where they would be exposed to mechanical
damage (godowns, engine rooms, rope and
motor alleys, etc); and

e) Where wet processes are carried out.

10.6.2 These systems shall generally be permitted
in office; and residential buildings. Appropriate
authorities may however specially permit their use
in industrial buildings of types other than those
indicated in 10.6.1.

10.7 Cleated Wiring System

10.7.1 This system shall be permitted for use in
industrial buildings for low tension circuits only,
with prior approval of appropriate authority.

10.7.2 When installed in bleaching or dyeing sec-
tions of a textile mills, the wiring shall be held by
porcelain bobbins secured to teak wood battens by
brass screws and the whole run inverted.

10.7.3 This system shall not be used for any type of
building of permanent nature other than of the kind
mentioned in 10.7.2.

10.8 Cable Trays or Wire or Bus Ducts

10.8.1 All cable trays or wire or bus ducts shall be
constructed from earthed sheet metal, enclosed or
open troughs with hinged or removable covers
housing and protecting either electric wires and
cables, installed at site, or factory mounted bare
conductors of aluminium or copper and shall be
capable of withstanding electro-mechanical stres-
ses.

10.8.2 Such systems shall be permitted under all
atmospheric conditions and all occupancies except
in following locations:

a) Where exposed to severe mechanical
damage;

b) Where exposed to corrosive vapours;

c) Where the atmosphere is likely to contain
flammable or explosive vapours;

d) Where wet processes are carried out; and

e) Where it is concealed.

10.8.3 The system shall be securely supported at
intervals not exceeding 1.5 m.

10.8.4 Such systems of totally enclosed type shall
be permitted to be extended vertically through
floors provided they are adequately protected

against mechanical damage up to a minimum dis-
tance of 2.5 m above working floor level.

10.8.5 Dead ends of all cable troughs or ducts shau
be closed.

10.8.6 Extensions and branches of such systems
shall also be of the same type.

10.9 Under Floor Cables Trenches (within
Buildings)

10.9.1 Such systems may be permitted under all
atmospheric conditions and in all occupancies
except where exposed to corrosive vapours and
locations where flammable/explosive vapours or
gases may be present, unless the cables or conduc-
tors are specially approved for such use or the
trenches are completely filled with sand.

10.9.2 Conductors or cables inside the trenches
shall be so mounted on insulated racks or other
supports as to be at least 75 mm above trench
bottoms.

10.9.3 The top of the trenches shall be covered
with removable concrete slabs or chequered plates.

10.9.4 In case of long trenches, it is recommended
that trenches of more than 1 000 cm cross-section-
al area be divided by incombustible barrier walls at
intervals not exceeding 45 m. Such barrier walls
shall be of at least 50 mm thickness and of the same
height as of the cable trench. The cables shall be
carried through holes in these barrier walls, which
shall be made good thereafter to prevent passage of
fire beyond the barriers (see also IS 12459).

NOTE — This provision need not be applied if the trenches
are completely filled with sand, pebbles, etc.

10.9.5 The combined cross-sectional area of all
conductors or cables shall not exceed 40 percent of
the internal cross-sectional area of the trench.

10.9.6 The trench shall be kept free of accumula-
tion of water, dust and waste materials.

10.10 Compartmentation of Cable Tunnels/
Galleries

The requirements for compartmentation of cable
tunnels/galleries should be as per IS 12459.

10.11 Flexible Cables and Cords

10.11.1 Flexible cables and cords shall be per-
mitted only as:

a) Pendants;

b) Wiring of fixtu res ;

c) Connections of portable appliances or
lamps;

d) Lift cables;

e) Wirings for cranes and hoists; and

8

IS 1646 : 1997

f) Connections to mains-operated electrical
stickers and motors mounted on parts of a
stationary machine, which undergo to and
fro motion during operation.

10.11.2 Where a lighting fitting is supported by
one or more flexible cords, the maximum mass to
which twin flexible cords may be subjected shall be
as follows:

Nominal Cross-

Number and

Maximum

Sectional Area of

Diameter

Permissible

Twin Flexible

of Lines, mm

Mass, kg

Cord, mm

0.5

16/0.2

1.7

0.75

24/0.2

2.6

1.0

32/0.2

3.5

10.11.3 Where flexible cables or cords are exposed
to risks of contact with oil or petrol or where cable
which will not support combustion is required, use
shall be made of cables or cords having a PVC or
oil resisting and fire retardant sheath.

10.11.4 Flexible cables and cords shall not be used
as fixed wiring unless contained in earthed metal or
any other non-combustible and mechanically
strong enclosure. This requirement need not, how-
ever, apply to short lengths of sheathed flexible
cable or flexible cord used as final connections to
fixed apparatus or for connections of control gear
of fluorescent lamps or discharge lamps. Non-
sheathed flexible cables and flexible cords shall not
be drawn into conduits or ducts.

10.11.5 Flexible cables or cords shall also not be
run through holes in walls, ceiling or floors or
through doors, windows or other similar openings.
Nor shall they be permitted to be concealed behind
walls, ceilings or floors.

10.12 Bare Conductors

10.12.1 Bare conductors are permitted for low ten-
sion side, of drawing frame transformer circuits
where the potential difference does not exceed 12
volts. Bare or lightly insulated conductors of extra
low voltage systems shall have adequate insulation
and further protection, where necessary, to ensure
that they do not cause risk of fire.

Bare conductors are also permitted for cranes and
hoists subject to special conditions laid down in this
code for such equipment.

10.13 Lightning Protection and Overhead Lines

10.13.1 The lightning protection system for build-
ings shall generally conform to IS 2309.

10.13.2 All overhead transmission lines, including
compound lines shall not be run above any process
or storage blocks or open storage site.

10.13.3 Lightning arresters shall be provided for
lines at both ends and at supports where exposed to
and liable to damage or injury from lightning. The
arresters shall preferably be of the non-horn type
for low and medium tension because of likely
damage by buds and distortion.

10.14 Wall Plugs and Sockets

10.14.1 All wall plugs and sockets in industrial
buildings shall be of metal clad 3 pin pattern
separately controlled by a switch, adjacent to the
wall socket.

NOTE — This shall not apply in case of wall plug and socket
with current ratings of 5 amp and less.

10.14.2 Where it is necessary to earth the metal
case of wall plug and/or portable appliances, the
connection shall be done with soldered or approved
lugs or crimped joints or any other approved means
of connection.

1 1 LIGHTING, FITTINGS AND ACCESSORIES

11.1 Fluorescent Lamp Fittings

11.1.1 These fittings may be one of the following

a) General purpose type — For use in office,
residences and similar locations.

b) Industrial type — For use in places where
dust, fly or corrosive vapours maybe present
(see Annex B for specification of fittings).,

c) Flame proof explosion type — For use in
places where flammable/explosive gases and
vapours are present.

NOTES

1 Where fumes or corrosive vapours or gases evolved due
•o chemical action, may be present, the reflector shall be of
vitreous enamel or non-combustible plastic and wiring shall
be in load-sheathed conductors. Rayon Spinning Sections
should have lead coated metal reflectors or equipment.

2 The position of fittings shall be carefully selected to avoid
any mechanical damage by belt drives, shafts, etc, and if
necessary suitable guards shall be provided. The fittings shall
be clear of the humidifier jets.

3 Where flammable/explosive gas or vapours may be present
the fittings shall be of flame proof type [ see IS 5572 (Part 1)
for classification of hazardous areas ].

11.2 Lighting Switchboard

11.2.1 Main switches and fuses shall be metal clad
and branch main board shall be metal clad when
used on medium tension circuits.

11.2.2 All equipment shall be of robust construc-
tion, of adequate dimensions and thoroughly dust
tight.

11.2.3 Each circuit from main distribution centre
except fuse distribution board shall be provided

IS 1646 : 1997

with a circuit breaker of linked switches and
cutouts.

11.2.4 Adequate means of control in approved
positions shall be provided for distribution boards
or a group of distribution boards which are fed from
a switchboard or distributing centre and within a
reasonable distance therefrom, such as one or more
boards erected in a room or building isolated from
source of supply.

11.2.5 Each final sub-circuit from a distribution
board shall be controlled by a single pole switch
connected to the live, outer or phase conductor.

11.2.6 Wood work shall not be used for mounting
of or construction of the frame work for iron clad
switch, distribution boards and control gear.

11.2.7 All equipment shall be numbered in English
and vernacular for ready identification and to indi-
cate the department, place or circuit controlled.

11.2.8 Circuits shall be arranged in symmetry as far
as practicable.

12 SPECIAL ELECTRICAL EQUIPMENT AND
APPLIANCES

12.1 Radio and Television Sets and Sound
Apparatus

12.1.1 The antenna of radio and television sets
shall be connected through a double pole change
over switch so connected that the antenna and the
set completely earthed when not in use of during,
thunderstorms.

12.1.2 The antenna shall be provided with a
suitable lightning arresters if situated in an area
subject to heavy thunderstorms.

12.1.3 All circuits (aerial and all internal wiring)
shall be so constructed that contact with any other
electric light and power circuits is impossible.

12.1.4 The lead-in conductor shall be of copper
and shall be not less than 2 mm in diameter.

12.1.5 The lead-in conductor shall enter the build-
ing through a non-combustible and non-absorptive
insulating bushing.

12.2 X-Ray Apparatus

12.2.1 The installation and precautionary
measures shall comply strictly with Rule 73 of
Indian Electricity Rules.

12.2.2 All such apparatus shall be located either in
independent detached building or in compartments
segregated by 355 mm thick brick walls with each
•opening protected by a fire resisting door/shutter.

12.3 Electrolyser Apparatus

12.3.1 Motor generator sets and/or separate gen-
erators and/or rectifiers together with necessary
switch and control gear shall be separated by blank
walls or located sufficiently away from the

electrolyser.

12.3.2 Circulating pumps and electrical equipment
thereof, where mounted in close proximity to the
electrolyser, shall be specially treated with anti-
corrosive paint at frequent intervals. The electrical
apparatus shall be of totally enclosed type or of an
equivalent type.

12.3.3 Windings and insulation generally shall be
specially treated to resist the corrosive effects of the
electrolytic fumes.

12.4 Electrostatic Charge Eliminators

12.4.1 Electrostatic charge eliminating devices
shall be provided for all high speed machines and
equipment of similar type where static electricity
may be developed, specially during dry seasons of
the year.

12.5 Cold Storage Buildings

12.5.1 The lighting inside cold storages shall be in
heavy gauged screwed steel conduit and water tight
fittings shall be used throughout.

12.5.2 Machinery and control gear
mounted external to cold storages.

shall be

12.6 Electrically Driven Fire Pumps for Hydrant
and/or Sprinkler Installation

12.6.1 In industry sufficient spare power shall
always be available to drive the fire pump set(s) at
all times throughout the year.

12.6.2 The power station and/or substation(s) sup-
plying power for fire pump circuit shall be so placed
that any falling masonry and the like from other
buildings occasioned by a fire or other cause cannot
damage the station and cut off power to the fire
pump circuits.

NOTE — It is preferable to locate the sub-station(s) at least
6 m away from all surrounding buildings.

12.6.3 A direct feeder, without any tappings shall
be laid from the substation to the pump house to
ensure that the supply to the pumping set(s) is
entirely independent of all other electrical equip-
ment in the premises viz, even when power
throughout the rest of the premises is switched off
the supply to the fire pumps remains available
uninterrupted. Overhead feeders to sub-stations

10

IS 1646 : 1997

supplying power to the fire pumps are not per-
mitted within a horizontal distance of:

a) 15 m of any process building/plant or tanks
containing flammable liquids, and

b) 6 m of any other building of tanks containing
non-flammable liquids or of storage in
open.

In case the feed to such sub-station is by means of
under-ground cables, the cables shall not pass
under any building or permanent structure.

12.6.4 Where there is more than one sources of
power for the operation of pumping set(s), the
electrical circuits shall be so designed as to ensure
that when necessary the set(s) shall continue to
operate without manual operation of any emergen-
cy switch, when the supply is interrupted.

12.6.5 Indicator lamps shall be fitted in prominent
position(s) both in the sub-station and pump
house, which would continuously glow as long as
power is available to the fire pump(s). A sound
alarm shall also be provided in the event of power
failure to the fire pumps.

12.6.6 The pump set(s) shall be of direct coupled
type, securely mounted on robust bed-plate(s), if or
horizontal type and should be free from vibrations
at all variations of load.

12.6.7 The motors of fire pumps shall be either of
totally enclosed or drip-proof type, the latter
having air-inlets and outlets protected with meshed
wire panels to exclude rodents, reptiles and insects.

12.6.8 The motors shall be wound for Class-E
insulation and the windings shall be vacuum im-
pregnated with heat and moisture-resisting varnish
preferably glass-fibre insulated, to withstand tropi-
cal conditions.

12.6.9 Motors wound for high-tension supplies
shall have a suitable fixed warming resistance to
maintain the motor windings in a dry condition at
all times and particularly under monsoon con-
ditions. The resistance shall be fed from medium
voltage circuits.

12.6.10 Heating apparatus shall also be provided,
when necessary, for medium tension motors where
they are located below ground level, in order to
maintain the motor winding in a dry conditions.
Adequate drainage shall also be provided in the
pump house in such cases.

12.6.11 The pumping set shall preferably be
housed in a separate building located at least 6 m
away from all other buildings and at least 15 m away

from units and/or storage tanks of plant handling
flammable liquids/gases.

12.6.12 The motor rating should be adequate to
drive the pump when operating on 150 percent of
rated flow.

12.6.13 The fire pump circuit shall be protected at
its origin by an automatic circuit breaker, from
which either the no volt coil is removed or which is
fitted with automatic re-setting type of no-volt coil,
and the overload setting shall be so adjusted as to
permit the motor to carry on overload of 50 percent
of its rated capacity.

12.6.14 Cables for motors of fire pumps and their
switchgear shall be armourd or shall be enclosed in
heavy gauge screwed steel conduit. Overhead lines
shall not be permitted within 6 m of window, door
or other opening in any of the protected building
or any other building within 15 m of a protected
building.

12.6.15 Equipment shall be painted throughout in
red or in orange yellow colour.

12.6.16 Pumping sets shall be worked for at least
15 min each week and records of the same shall be
maintained.

12.6.17 The incoming cable to the fire pump room
shall terminate in an isolating switch fuse unit
incorporating HRC fuses and where necessary
provided with distribution system.

12.6.18 The starting switchgear for the fire pumps
should be suitable direct on line starting but other
alternative arrangements are acceptable with the
approval of competent authority.

13 REQUIREMENTS FOR SPECIAL
OCCUPANCIES

13.1 Hazardous Locations

For the purpose of this code a location shall be
regarded as hazardous where any one or more of
the following conditions exist:

a) Where flammable gases or vapours may be
present in the atmosphere in sufficient
quantities to produce explosive or
flammable mixtures;

b) Where combustible dust is produced or
handled; and

c) Where vegetable or viscose, acrylic and
nylon 66 fibres are processed or handled.

13.1.1 In locations where the atmosphere may
contain flammable gases or vapours the clas-
sification of areas and selection of Electrical

11

IS 1646 : 1997

Equipment permitted to be installed therein shall
be governed by IS 5572 (part i) and IS 5571
respectively. These requirements may, however, be
modified in any particular situation as per the
provisions of 13.1.3.

13.1.2 In case of process or operations involving
combustible liquid(s), the presence of flammable
vapour in the atmosphere maybe deemed probable
only if the flash point of the liquid(s) is below
32.2°C. However, locations where combus-
tible/flammable liquids having flash points above
32.2°C but not above 93.3°C are handled shall be
regarded as hazardous if such liquid is (a) sprayed
or (b) present in the form of mist or (c) heat to or
above its flash point.

13.1.3 Wherever possible, the hazardous locations
where installation of flameproof electrical equip-
ment and fittings is required shall be located either
in a detached building or in a compartment
segregated from the remainder of the premises at
least by a non-combustible fire resisting wall of 2 h
rating without any kind of opening. Areas where,
however, this is not practicable, shall be demar-
cated by fencings, railing or boundary lines painted
on floor and all electrical equipment and fitting
shall be of flameproof type within the hazardous
location as also up to a distance from the boun-
daries of the demarcated area indicated hereunder:

a) Where the processes or operations neces-
sitating the use of flame-proof equipment
and fittings are carried out in the open.

All space within 6 m horizontally in any
direction from the demarcating fencing/
railing or boundary line and 3 m vertically
above the highest hazard source.

b) Where the processes or operation neces-
sitating the use of flame-proof equipment is
carried out in enclosed space of equipment,
as in the case of paint spray booths, baking
or drying ovens, enamelling or coating
equipment, etc.

All space within 6 m horizontally of open
face or door opening of such equipment and
3 m vertically above the roof of such equip-
ment.

13.1.4 Except the wiring of rigid metal conduits
and armoured cable wiring, no electrical equipment
or fittings shall be permitted where it mav be sub-
jected to hazardous accumulation of readily ig-
nitable deposits or residue, as within a spray
painting booth or drying oven.

13.1.5 Illumination of spray painting booths or
similar coating or finishing equipment through
glass panels is permitted, provided the:

a) lighting fittings are of fixed type and in-
stalled behind giass panels;

b) glass panel(s) is so sealed, that, it effectively
isolates the lighting equipment from the
hazardous area;

c) panels are so located that deposits of haz-
ardous residues on them are avoided as far
as possible; and

d) glass used for panel is either of the wired or
specially toughened type.

13.1.6 Electrical installation in hazardous
locations involving presence or use of combustible
dust or fibre (vegetable, animal or synthetic) shall
comply with the following special provisions:

a) Wiring methods — The type of wiring
methods permitted shall be as follows:

Screwed steel or rigid metal conduits,
mineral insulated or other sheathed
cables, armoured cables and enclosed
metal covered cable or bus ducts.

b) Motors — Motors shall be either of totally
enclosed, or totally enclosed fan-cooled or
dust tight type.

c) Distribution and panel boards — Location of
distribution and panel boards where
combustible dust is evolved shall be avoided
as far as possible.

d) Switchgears — In areas where combustible

Hnct tnav lv» niv»cpTit nil r-irr-nit hrpatprc

shall be preferred.

e) Lighting fittings — Use of incandescent
lamps shall be avoided as far as practicable
and the fluorescent light fitting used shall be
of industrial type.

f) In case of incandescent lamps being used,
the fitting shall be enclosed in dust tight
enclosures.

g) The leads from ceiling rose to lamp ter-
minals shall be enclosed in conduits.

13.2 Lifts

13.2.1 The installation of lifts and care of electrical
installation shall fully comply with relevant
provisions of IS 1860 and IS 4666.

13.3 Petrol Station

13.3.1 Electrically operated valves shall be so
designed that they can also be manually operated.

13.3.2 The valve or valves shall close automatically
when the electric supply ceases.

13.3.3 All fusible links in the circuit supplying the
valve or valves shall be in series and on the live lead.

13.3.4 The circuit in which the possible links form
a path for the current to the fire valve shall be a

IS 1646 : 1997

separate final sub-circuit controlled by a switch and
by a fuse not exceeding 5 A capacity both on the line
lead.

13.3.5 Equipment shall be of certified 'flame
proof type unless it is separately mounted and is
away from any possible source of fumes.

13.4 Cinematographic Projection and Rewinding
Rooms

13.4.1 Where general lighting of the auditorium
and exits can be controlled from within the
enclosure, separate and independent means of
control shall also be provided outside the enclosure
and well away from it.

13.4.2 All switches, fuses and connections thereof
shall by totally enclosed and iron-clad and all
electric lamps and resistances so protected as to
avoid their possibility of coming into contact with
or in close proximity of films or other combustible
materials. Resistance connected with auditorium
or stage lighting shall not be located in the projec-
tion or rewinding rooms.

13.4.3 The insulating material of all electric cables
including leads to lamps shall be covered with fire
resisting material.

13.4.4 There shall be no unnecessary and loose
electric cable. The 'leads' to the projector lamps
shall be taken as separate circuits from the source
of supply and from the supply side of main fuses in
general lighting circuit. Efficient switches and
fuses shall be inserted at the point where the supply
is taken, and, in addition, an efficient double pole
switch shall be fitted in the cinematograph lamp
circuit inside the enclosure. When the
cinematograph lamp is working the voltage across
the terminals of the double pole switch inside the
enclosure shall not exceed 110 volts.

13.4.5 Cables from projector lamps should be
taken as separate circuits from the source of supply
and from the supply side of main fuses in general
lighting circuit. Efficient switches and fuses should
be inserted at the point where the supply is taken,
and in addition, an efficient double pole switch
should be fitted in the cinematrograph lamp circuit
inside the enclosure when the cinematograph lamp
is working the voltage across the terminals of the
double pole switch inside the enclosure should ex-
ceed 110 volts.

13.4.6 Resistances shall be made entirely of incom-
bustible material and shall be so constructed and
maintained that no coil or other part shall at any
time become undully heated. All resistances, with
the exception of a resistance for regulating pur-
poses shall be placed outside the enclosure and, if

reasonably practicable, outside the auditorium. If
inside the auditorium, they shall be protected by a
wire guard or other efficient means of preventing
accidental contact.

13.4.7 The operator shall satisfy himself before the
commencement of each performance that all
cables, lead connections and resistances are in
proper working order. The resistance shall be
inspected at least once during each performance. If
any fault is detected, current shall be immediately
switched off and shall remain switched off until the
fault has been remedied.

13.5 Accumulator or Battery Service Stations

13.5.1 Charging shall be carried out in well venti-
lated situations and no smoking or naked lights
shall be allowed.

13.5.2 Accumulators/batteries shall stand directly
or non-ignitable, non -absorbing, non-conducting
material, such as glass, porcelain or glazed earthen-
ware. These materials shall rest on a bench which
shall be kept dry and shall be insulated from earth,
or constructed of wood. It shall be of slat formation
and treated with anti-sulfuric enamel.

13.5.3 The accumulators shall be so arranged on
the bench that a potential difference exceeding 12
volts shall not exist between adjacent cells. The
bunching of accumulators or arranging them in
circular formation shall not be allowed.

13.5.4 All combustible material within a distance
of 60 cm measured horizontally, or within 2 metres
measured vertically, from any accumulator shall be
protected by asbestos sheets.

13.5.5 The charging circuit shall be provided with
double pole switches and fuses, and, where a motor
generator is employed the motor shall be provided
with double pole switches and fuses and an auto-
matic battery cut-out shall be placed in the gener-
ator circuit. Any sub-circuit shall be provided with
a fuse rated at not more than 7 A in each live
conductor.

13.5.6 Charcino control nanels shall be of durable
non-ignitable, non-absorbent, non-conducting
material and together with the rectifiers, trans-
formers and supports for resistances of lamps, shall
preferably be fixed to brick or similar wall. If,
however, they are fixed to wood work, such wood
work shall be covered with hard-asbestic sheets or
similar fire-resistive material.

13.5.7 If accumulators are charged through resis-
tance coils or lamps, such resistance coils or lamps
shall be at least at distance of 60 cm from the
nearest accumulator.

13

IS 1646 : 1997

13.5.8 All wiring shall be securely mounted and
protected against mechanical injury and efficient
terminal or connections shall be provided from
which the connections to the accumulators can be
made. Rubber or P.V.C. insulated wiring, if on
insulators shall not be run in such a position that a
fire arising at any accumulator could reach it. All
conductors connecting supply terminals to the
accumulators shall have either rubber or tough
compound insulation without a tape or braid.

13.5.9 If the supply is taken from mains having one
conductor earthed, the lamps or other resistances
shall be connected on non-earthed lead and the
accumulators connected direct to earthed conduc-
tor. Precaution shall be adopted to prevent the
attendant receiving shocks.

13.5.10 Celluloid-cased accumulator shall not be
kept on charge at any time without an attendant.

13.5.11 Spring-jacks shall be used for final connec-
tion to the accumulator terminals.

13.5.12 All insulators shall be kept as dust free as
practicable.

13.6 High-Rise Buildings

13.6.1 All electric distribution cables/wiring shall
be laid in a separate fire resistant duct. The duct
shall be sealed at every floor with non-combustible
materials having the same fire resistance as that of
the duct. Low and medium voltage wiring running
in shafts and in false ceiling shall run in separate
conduits.

13.6.2 Separate circuits for water pumps, lifts and
staircase and corridor lighting and blowers in
pressurising system shall be provided directly from
the main switchgear panel and these circuits shall
be laid in separate conduits so that fire in one
circuit will not affect the others. Master switches
controlling essential service circuits shall be clearly
labelled.

13.6.3 Staircase and corridor lights shall be on
separate circuits and shall be independently con-
nected so that it could be operated by on switch
installation on the ground floor easily accessible to
fire fighting staff at any time.

13.6.4 A standby electric generator shall be in-
stalled to supply power to staircase and corridor
lighting circuits, fire lifts, the electrically operated
fire pumps, pressurising fans and blowers in case of
failure of normal electric supply.

13.6.5 If more than 200 litres of oil are contained
in any oil immersed electric gear a retaining sill
threshold shall be provided around the gear or at
the door.

14 GODOWNS

14.1 General

Wiring shall either be in rigid steel conduits or
armoured cable. Wall brackets shall be eliminated
and rod pendants and batten holder fittings shall be
erected for the lamps which shall be of a type
protected against mechanical damage. Industrial
type fluorescent light fittings shall, however, be
permitted. The fittings for lamps shall be fixed at
sufficient height above the highest level of bulk or
other goods which are stored in the godown. The
circuit shall be controlled by a linked switch and
cut-outs which shall be placed outside the godown
in a convenient portion.

14.2 Raw Jute Godowns

14.2.1 The supply of electricity shall be at low
voltage, that is, not exceeding 250 volts.

14.2.2 All wiring shall be encased in screwed steel
conduits, the horizontal portions of which shall be
sloped to allow condensed moisture to collect at set
places where drainage outlets shall be provided.
Such outlets shall be properly secured, against
entry of insects, etc.

14.2.3 The cable used shall not be of less than
3/.029 size of 250-V grade and shall be of single
core, rubber or PVC insulated, taped and branded.

14.2.4 No joint boxes or cut-outs of cables shall be
allowed inside the godown.

14.2.5 The conduit shall be affixed to (not recessed
into) walls or roofs of godowns by means of saddles
grouped on walls or roofs, the distance between
saddles not exceeding 750 mm. All conduits must
be laid externally on the outside walls or roofs of
the godown except those lengths which are required
to carry the cables to light fittings. In the latter case,
the conduit should be run above the level of highest
stacking.

14.2.6 Only bulkhead light fittings of approved
design with CI. frames of robust construction and
bulkhead glasses protected with thick steel lined
guards shall be used.

14.2.7 Each lighting fittings shall be affixed to the
wall or at not more than 450 mm below the roof of
the godown. In case of a sprinklered godown each
lighting fitting shall either be above the level of the
sprinkler heads or not less than 300 mm below that
level, it being understood that in no case shall a
light fitting be installed low than 750 mm above the
maximum stacking height.

14.2.8 All lights in the godown shall be controlled
by one or more double pole metal-clad switches and

14

IS 1646 : 1997

fuses situated outside the godown in a convenient
place and effectively protected from weather.

14.2.9 An indicator light controlled by the
switch(es) shall be provided on the switch panel to
show whether the lights inside the godown are on
or off when the godown is closed and locked.

14.3 Strong Rooms

14.3.1 Permanent lighting shall be provided by
means of concealed wiring or solid drawn conduit
wiring with the main switch located outside.

14.4 Nitrocellulose (and Chemicals Having
Similar Fire Hazard Characteristics) Godowns

14.4.1 Lamps in nitrocellulose storage rooms shall
be rigid fixtures of glass enclosed and gasketted type
or flameproof fluorescent fittings. Lamps shall be
controlled by a switch having a pole in each un-
earthed conductor. This switch shall be located
outside the room and provided with a pilot light to
indicate whether the switch is 'on' or 'off. This
switch shall disconnect from all sources of supply
all unearthed conductors terminating in any outlet
in the room.

14.4.2 No socket outlets, electric motors, heaters,
portable lights or other portable electric equip-
ment shall not be located in nitrocellulose storage
rooms.

15 TESTING

15.1 The electrical installation in a new building or
an addition to an existing installation shall be tested
as per IS 732 before it is put to service. The instal-
lation shall also be checked periodically as decided
by the appropriate authority.

15.2 The following tests shall be carried out as
required by the appropriate authority:

a) Full load and/or flash tests of rotating
machinery, transformers, condensers,
rectifiers, etc.

b) Insulation resistance tests of rotating
machines, transformers, condensers,
regulators, cable circuits, etc, by meggers of
appropriate voltage.

c) Lighting circuits shall be tested in following
manner:

1) All switches 'on' and consuming
devices in circuit, both poles con-
nected together to obtain resistance to
earth;

2) Between poles with lamps and other
consuming devices removed and
switches 'on'; and

3) With lamps and other consuming
devices in position but switches 'off.

d) Earth continuity tests.

e) Power circuits to be tested between phases
or outer and middle or neutral wires and to
earth.

15.3 The appropriate authority shall have the right
to vary the foregoing tests or carry out further tests
as may be considered necessary.

16 INSPECTION

16.1 All electrical inspections shall be inspected,
periodically and proper vigilance shall be kept.
Any faults or defects that are notice shall be at-
tended to and the defects rectified immediately.

15

IS 1646 : 1997

ANNEX A

(Clause 2)

LIST OF REFERRED INDIAN STANDARDS

IS No. Title

732 : 1989 Code of practice for electrical

wiring installations (third
revision)

1860 : 1980 Code of practice for installation,

operation and maintenance of
electric passenger and goods lifts
(first revision)

2309 : 1989 Code of practice for the protec-
tion of buildings and allied struc-
tures against lightning (second
revision)

2667 : 1 988 Fittings for rigid steel conduits for

electrical wiring (first revision)

3043 : 1987 Code of practice for earthing

4013 : 1967 Dust-tight electric lighting fit-
tings

IS No.
4666 : 1980

Title

Electric passenger and goods lifts
(first revision)

5571 : 1979 Guide for selection of electrical

equipment for hazardous areas
(first revision)

5572 : 1994 Classification of hazardous areas
(other than mines) having flam-
mable gases and vapours for
electrical installations (second
revision)

9537 Conduits for electrical installa-

(Part 3) : 1983 tions: Part 3 Rigid plain conduits
of insulating materials

12459 : 1988 Code of practice for fire-protec-
tion of cable runs

16

IS 1646 : 1997

ANNEX B

{Clause 11.1.1)

FLUORESCENT LAMP FITTINGS

B-l GENERAL PURPOSE TYPE FITTINGS

B-l.l The general design of reflectors shall be of
suitable type and material. The material shall be
any suitable metal or plastic. If plastic of a combus-
tible nature is used, it shall not be in contact with
any electrical conducting part and shall not ignite
by the radiation from the lamp.

B-1.2 The auxiliary equipment, that is, choke coil,
power-factor condenser and stating unit (compris-
ing thermal switch, radio-suppresser condenser)
shall comply with relevant Indian Standards
Specifications and shall preferably be mounted on
the lamp fitting itself in a dust-tight enclosure, but
if any item is mounted separately it shall be
mounted on parts made of non-combustible
material.

B-1.3 The wiring connections between the equip-
ment, that is, chockes and condensers, shall be in
PVC insulated wiring, properly clamped as neces-
sary.

B-1.4 The suspension shall be made by two con-
duits or rods or robust chains, spaced to share
equally the weight of the fitting.

B-1.5 The lamp or tube holders may be of plastic
material provided these are of efficient and ap-
proved design, and that each tube is securely held
by suitable metal spring clips at each end.

B-1.6 Earthing of the fixture shall be made with an
unbroken conductor, the suspension chains (where
employed) shall not be regarded as an approved
means of earthing.

B-1.7 Fluorescent fixtures may be suspended from
conduit wiring junction boxes as a means to prevent
exposure of conductors from the fitting to the
wiring in the conduit. The connection inside the
junction box shall be made to a porcelain junction
base. Plain procelain connectors shall not be per-
mitted in the box.

B-2 INDUSTRIAL TYPE FITTINGS

B-2.1 Mild steel trough suitably enamelled or
painted or any other robust reflectors shall be used
which may, if necessary, have upward lighting slots.

B-2.2 The auxiliary equipment, that is, choke coil,
power-factor condenser and starting unit (compris-
ing thermal switch and radio-suppresser con-
denser) shall conform to relevant Indian Standards
and shall be mounted on suitable framework in a
separate detachable dust-proof non-ventilated box,
with tight fitting covers securely fixed by machine
screws and bolts to the main trough.

B-2.3 The wiring connections between the equip-
ment housed in the choke and condenser box shall
be vulcanised rubber insulated flexible cabling or
approved PVC insulated conductors in heavy
gauge, welded or solid-drawn steel conduit, or run
internally and properly clamped.

B-2.4 Suspension shall be made by two conduits
spaced to share equally the weight of the fitting.
Each conduit rod shall be provided with a spring
loaded ball-and-socket joint ceiling plate at the top,
and the other end shall be bolted to the trough.

B-2.5 Lamp or tube holders shall be made of plas-
tic, provided an efficient and approved design is
employed and each tube is held with suitable metal
spring clips at each end.

B-2.6 Earthing of fixtures shall be made with an
unbroken conductor.

B-2.7 Fluorescent fixtures may be suspended from
conduit wiring junction boxes, as a means to
prevent exposure of conductors from the fitting to
the wiring in the conduit. The connection inside
the junction box shall be made to a porcelain junc-
tion base. Plain procelain connectors shall not be
permitted in the box.

B-2.8 The chokes of all fluorescent fittings shall be
mounted on incombustible material.

B-2.9 Incoming twin twisted flexible conductor
shall enter the side of the box through a dust-tight
bushed hole.

B-2. 10 The lighting tubes and reflectors shall
be kept clean to obtain maximum efficient light.
Cleaning shall be carried out by competent per-
sonnel.

17

IS 1646 : 1997

ANNEX C

(Foreword)

FIRE SAFETY SECTIONAL COMMITTEE, CED 36

Chairman
Shri J. N. Vakil
Members
Shri K. Ravi {Alternate to

Shri J.N. Vakil)
Dr A. K. Bhalla

Dr K. S. Uppal {Alternate)
Shri M. M. Kapoor

Shri Rana Pratap {Alternate)
Shri S. N. Chakraborty

Shri P. K. Majumdar {Alternate)
Chief Fire Officer
ShriS. M. Desai

Shri Ramesh Dhobley
Shri S. K. Dheri

Shri R. C. Sharma {Alternate)
Shri K. P. Sharma

Asstt Security Commissioner {Alternate)
Fire Advisory

Dy Fire Advisor {Alternate)
Shri J. S. Gahlaut
Shri P. N. Ghosh
Shri C. P. Gosain
Shri S. C. Gupta

Shri Sanjeev Angra {Alternate)
Shri S. K. Shangari

Lt-Col A. T. Parnaik
Shri G. B. Menon
Member (Hydro - Construction Monitoring)

Chief Engineer (HTD-II) {Alternate)
Shri V. B. Nikam

Shri D. Padanabha

Shri B. S. Venkatesh {Alternate)
Shri P. N. Panchal

RetdDy Inspector General (Fire) CISF
President

Shri V. M. Ranalkar
Shri R. N. Chachra
Shri A. R. Khan

Shri NaTARajan {Alternate)
DrT. P. Sharma

Dr Gopal Krishnan {Alternate)
Shri R. sundarajan

Shri S. K. Chattopadhayay {Alternate)
Shri M. S. Tyagi

Shri P. K. Saksena {Alternate)
Managing Director

Shri T, V. Madhumani {Alternate)
Shri K. K. Sharma,
Director (Civ Engg)

Representing
Tariff Advisory Committee, Mumbai

Ministry of Defence (CEESO), New Delhi

Engineers India Ltd, New Delhi

Tariff Advisory Committee, Chennai /Calcutta

Municipal Corporation of MumbaiMumbai Fire Brigade), Mumbai
In personal capacity {B-4I5A.G. KhanRoad

Municipal officers Society, Worli, Mumbai)
Bhabha Atomic Research Centre, Mumbai
Delhi Fire Service, Government of Delhi, New Delhi

Ministry of Railways, New Delhi

Ministry of Home Affairs, New Delhi

State Bank of India, Mumbai

In personal capacity {J-1916, Chittaranjan Park, New Delhi 19)

Central Public Works Department, New Delhi

Lloyd Insulations (India) Pvt Ltd, New Delhi

Engineer-in-ChieFs Branch, New Delhi

In personal capacity {AS, Puzhakkara Padam, Vennala, Cochin)
Central Electricity Authority, New Delhi

In personal capacity {4/34, Haji Ali Municipal Officers Cooperative

Housing Society, Mumbai)
Tata Consulting Engineers, Mumbai

In personal capacity {46, Block E-l, Pocket-11, Sector IS, Rohini, Delhi)

Institution of Fire Engineers (India), New Delhi

Ministry of Petroleum and Natural Gas

Metallurgical and Engineering Consultants (India) Ltd, Ranchi

Bharat Heavy Electricals Ltd, Bhopal

Central Building Research Institute, Roorkee

National Thermal Power Corporation Ltd, New Delhi

Ministry of Labour (Regional Labour Institute, Kanpur), New Delhi

Loss Prevention Association of India Ltd, Mumbai

Director General, BIS
{Ex -Officio Member)

Member Secretary

S. Chaturvedi

Dy Director (Civil Engg), BIS

18

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote
harmonious development of the activities of standardization, marking and quality certification of goods and
attending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any form
without the prior permission in writing of BIS. This docs not preclude the free use, in the course of
implementing the standard, of necessary details, such as symbols and sizes, type or grade designations.
Enquiries relating to copyright be addressed to the Director (Publication), BIS.

Review oflndian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed
periodically; a standard aiong with amendments is reaffirmed when such review indicates ihat no changes are
needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards
should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue
of 'BIS Handbook' and 'Standards Monthly Additions'.

This Indian Standard has been developed from Doc: No. CED 36(5418).

Amendments Issued Since Publication

Amend No.

Date of Issue

Text Affected

BUREAU OF INDIAN STANDARDS

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